The invention relates generally to a ferrite particle collection apparatus for removing entrained ferrous particles from a material flow. Specifically, the invention relates to a magnetic collection apparatus having a material flow passage including at least a magnetic ferrous particle collector in the form of a rotatable magnetic roll or drum located within the passage. The magnetic roll or drum is caused to rotate in contact with the material flow having entrained ferrous particles.
The material having the entrained ferrous particles is fed into the apparatus and caused to come into contact with the magnetic roll or drum. The material passes over and around the magnetic roll or drum, and the entrained ferrous particles are removed from the material flow by attraction to the magnetized surface of the roll and subsequently wiped or cleaned from the roll into a final collection area.
Many commercial processes involve temporary storage, transfer, and handling of bulk material or material flows, both liquid and dry product, during manufacture which subject the bulk material or material flow to equipment having or made from iron or iron compounds. During such commercial processes, metallic articles, pieces of iron, or material containing iron or other ferrous particles may break free from the equipment and be entrained in the material or material flow. Also, metal items or articles may be deposited, dropped or fall into the bulk materials from sources extraneous to the processes e.g. workers tools, jewelry or other personal items,often find their way into such bulk material manufacturing processes.
These articles and particles are undesirable in most all manufacturing situations. Iron particles in food processing are particularly undesirable, both from a health/cleanliness viewpoint and from the potential for damage to processing equipment caused by the iron particles. Numerous methods to remove the iron have therefore been developed, including magnetic deposition. However, magnetic deposition methods in use have drawbacks due to the configuration of the magnets in conjunction with other component parts.
Separator equipment using magnets to remove iron particles by deposition is well known in the art. Examples include magnetic drums, magnetic pulleys, and tube magnets. Magnetic drums in use have a (partial or half round 180 degree) stationary magnet inside a rotating cylinder to separate ferrous from non-ferrous material passed over the drum surface. Expensive strong rare earth magnets are valuable due to the concentration of magnetic flux on the surface and close to the surface. Magnetic drums suffer in efficiency because of the extra air gap between the stationary magnet and the rotating cylinder wall. Rare Earth Magnetic strength is reduced due to the additional air gap, therefore efficiency of particle collection is reduced. Magnetic drums create rotating air currents that often allow a high percentage of non ferrous powdered product to infiltrate the iron collection area. Magnetic drums discharge the ferrous fraction along their entire length adding to this product loss. This limits the magnetic application and or is costly by the loss of product. It is not uncommon to find powdered product loss due to this phenomenon to be 30% or higher.
Magnetic pulleys have a similar drawback. Magnetic pulleys utilize a belt to transfer the bulk material with entrained ferrous particles past a stationary magnet. Due to the distance of the magnetic pulley from the top of the belt where the contamination and product are present, the magnetic strength necessary for particle attraction is reduced in relation to belt thickness.
Self cleaning (easy clean) tube (grate magnets) require a series of non-ferrous wipers to slide ferrous material to dead zones present at one end for release. The collected iron is physically pulled across alternating north south poles against the natural polarity force. (Magnetic separators sometimes use this principal to purify a ferrous iron powder product by causing the iron powder to jump magnetic fields enabling it to release less magnetic particles. Moving ferrous material by traveling along north south poles is more desirable because one is working with natural forces and iron or paramagnetic iron are less likely to be accidently discharged into the product.
Self cleaning tubes (grates) have more parts to wear due to friction, they are more complicated by design due to the number of parts and precision fit wipers on the tube, are difficult to manufacture, have higher maintenance requirements, are not as magnetically strong due to their limited size, and handle less capacity of product due to the grate configuration of tubes typically 1xe2x80x3 tubes on 2xe2x80x3 centers. The ferrous particles are required to be forced against alternating magnetic fields for removal. This often requires considerable force when rare earth Neodymium-Iron Boron Magnets reaching MGOe 30 to 45 strengths are used. Also, where large volumes of iron are present on a tube, the force required to wipe or pull the iron across the tube becomes impractical.
To overcome the above drawbacks of existing ferrous particle removal devices, it is therefore an object of the invention to provide a magnetic roll with high magnetic strength, to maximize entrained ferrous particle removal. This is accomplished with the claimed invention having one or more magnets forming or in contact with a specifically defined portion of the roll surface.
It is a further object of the invention to provide for simpler yet more effective removal of the ferrous particles after their attachment to the roll. This is accomplished with the roll surface having a magnetic collection surface portion formed as a contiguous surface, similar to a screw shape, about the surface of the roll. The collection spiral portion can be magnetically induced into a magnetically attractive state by a plurality of magnets in contact with the collection spiral, wherein one or more magnets in direct contact with the collection spiral create exposed magnetic poles of the outer face of the spiral.
Another object of the invention is to capture and collect a substantial amount of ferrous particles or articles on the magnetic poles of the outer surface of a roll having a spiral, and although magnetic poles themselves are not new, in the spiral shape of the claimed invention, they permit a greater opportunity to attract and retain captured ferrous material under an outside influence to along the length of the roll and easily follow the direction of the spiral to a discharge end of the roll for removal and collection.
It is a further object of the invention to permit a more complete removal of the captured ferrous material from a roll, one way is by reducing the magnetic field strength locally at a discharge end of the roll which locally reduces the forces holding the particles on the roll wall and allows the particles or articles to be collected in a collection area.
A yet further object of the invention is to provide a simple mechanical wiping or cleaning system for the roll. This is accomplished in the claimed invention by providing a barrier, wiper or scraper of a non-magnetic material or fluid flow, the wiper having a length closely matching that of the roll. By bringing the barrier, wiper or scraper into contact with a part of the roll surface over the entire length of the roll, and rotating the roll against such an obstruction the captured ferrous material is driven in an auger-like motion towards the discharge end.
According to the invention there is provided an apparatus for removal of entrained ferrous particles from a desired material, through magnetic attraction, comprising an inlet and an outlet defining a material flow way therebetween; a magnetic roller positioned in the material flow way, the magnetic roller having an outer surface defining a radially attractive magnetic field along a portion of the outer surface of the roller.
Also according to the invention there is provided an apparatus for removal of entrained ferrous particles from a desired material, through magnetic attraction, comprising at least one spiral magnetized by inducement each said spiral being formed as a roll assembly comprising at least one magnet positioned in the continuous pitch gap at least one non-ferrous material bonded to an outside surface of the at least one magnet within the pitch gap and a continuous exposed outer surface of the spiral each roll assembly having a central longitudinal axis of rotation each roll assembly rotates about its axis of rotation at a preselected rotation speed and each roll assembly having at least one scraper of a non magnetic material for removal of said particles from each said roll assembly wherein the material containing ferrous particles being passed in close proximity to each said roll assembly, the ferrous particles being magnetically captured by each said roll assembly, the captured particles being subsequently removed from each said roll assembly by said rotation of each said roll assembly against an obstruction, and said captured particles transfer to an end of each said roll by a continuous obstruction contact along the roll assembly.
According to the invention there is also provided a method for removal of entrained ferrous particles from a desired material, through magnetic attraction, comprising the steps of creating a magnetic field along a non-linear portion of an outer surface of a cylindrical roller; positioning the cylindrical roller in a material flow; attracting ferrous particles from the material flow onto the non-linear magnetized portion of the outer surface of the roller; rotating the cylindrical roller relative to a linear obstruction substantially in contact with the outer surface of the roller to force the ferrous particles along the non-linear magnetic field of the outer surface of the cylindrical roller towards an area of reduced magnetic field; and removing the attracted ferrous particles from the outer surface of the roller.